http timestamp auto data file redownload

warning: delete file on web server will not trig the judge to delete

git-svn-id: http://hustoj.googlecode.com/svn@2200 19ab8b60-bd6c-11dd-baed-41e496641fac
auto download file refresh

git-svn-id: http://hustoj.googlecode.com/svn@2201 19ab8b60-bd6c-11dd-baed-41e496641fac